I agree with Lill - whatever is happening or happens, the best thing you can do is give up smoking tobacco. Now that a range of nicotine products are available - including the very effective and 95% less harmful e-cigs - its now a lot easier to give up this habit.
I would ask for another spiromety to be done in a few weeks time when the coughs gone. If you've had a bit of a chest infection it's bound to have affected the results.
But even if it is COPD, it sounds as though its border-line, so I wouldn't fret too much. You're young .. and otherwise healthy, and you should be just fine if you DON'T START SMOKING AGAIN! You've had a wake-up call .. heed it.
Vape if necessary .. but please don't go back on the fags. They WILL kill you.
Exercise every day (even if it's just a brisk 10 minute walk), eat healthily, take your meds, learn to breath properly, (lots of Youtube videos on breathing properly) and DON'T stress out. The very WORSE thing you can do is worry about it. Get out there and enjoy your life!
In December 2015, Harvard University released a study.
It can be found in the Journal Sentinel, December 2015, titled 'Harvard study confirms dangers of vaping"
The first paragraph is such;
"Harvard University scientists are calling for "urgent action" after their federally funded study confirmed dangerous, lung-destroying chemicals are commonly found in the liquids used in electronic cigarettes and other vaping devices."
Anything other than clean air is dangerous to inhale.
Of course it's better to inhale nothing at all .. you'e right lill. But my point is that vaping is infinitely safer than smoking, and is an option for those struggling to give up the dreaded weed. And in any case, many vaping liquids these days do not contain 'diacetyl'.. the compound mentioned in the study you quoted.
On reading what you have communicated ikwz, FEV and FVC amount seem above average to me, ie excellent measurements.
But if your doctor said you are 1 or 2% lower than the normal result expected that may be, but to me your being prescribed symbicort doesn't seem to add up with what you have communicated although I suspect your doctor knows what may be right for you, perhaps your doctor feels you have uncontrolled asthma which needs treating, since you mention to lill that your doctor has not indicated you have COPD, either way, asthma, or any other respiratory or health issue, stopping smoking is very good advice.
Not sure if you are saying you have been a smoker for 8 years, or a smoker since you were 8 years old, if the latter there is every chance you have damaged your lungs through smoking at such a young age before your lungs / body was fully developed.
On the other hand with such good FEV1 and FVC percent you are doing very well. For a comparison, my brother lives in London (he is much older than you) his respiratory nurse says most people living in London will have a reduced lung function of around 2% due the the pollution levels in the city.
If you have a copy of your spirometry results you may want to double check them using patient uk spirometry calculator, just include your age height, FEV FvC etc.
For example a 23 year old female, height of 162 cm with FEV and FVC same measurement as your own would calculate as normal.
Hope you find the symbicort helps with your cough and you are successful in stopping smoking so that in another 23 years you can avoid any diagnosis of COPD.
The other things I thoroughly detest about vaping are that it perpetuates the cig-holding habit/hand to mouth motion habit/putting something unhealthful in the mouth habit, and that it often means ex-smokers cannot avoid seeing others who look like they're smoking in places which are officially non-smoking zones. All this goes to that slippery slope concept.
After 7 smoke-free years, I still have to be very careful about watching people smoke or vape, whether that's for real or in a movie or tv show. I know from my 1st "quit" that being near or watching someone else smoking is dangerous for me, especially if the smoker appears to enjoy it even 1/2 as much as I always did.
So my opinion is that no one should use vaping as an attempt at quitting.